Pluto No Longer a Planet

[Terrell]

There is going to be planets found that is going to bust this thing all over the place.

1# Planets moving 5 or 6 SOL in then out from there sun.
2# Planets floating through space.

Planets that are slightly smaller then Mercury. In which will give us a hard time with this thing.

This can only lead to a mess. There is common sense reasons why pluto should remine a planet. Because whats a planet in whats a darf?

The first thing isn't a problem for the definition of "Planet" a body big enough to be deserving of planet status will clear out it's orbital path of most bodies (IOW it won't be a member of a belt of objects) regardless of whether it's orbiting a star or not, and how elliptical a planet's orbit is especially since all planets orbits are elliptical according to Keplers laws of Planetary motion (see wiki article below). Pluto doesn't clear out the Kuiper belt of objects beyond Neptune, it's a member of the group and isn't substiantally different from the other Kuiper belt objects.

BTW the unit of distance you're looking for isn't SOL (that's the Sun's name) it's AU for Astronomical Units or AU. 1AU= 93 million miles.
http://en.wikipedia.org/wiki/Astronomical_unit

Kepler's first law
The orbit of a planet about a star is an ellipse with the star at one focus.

There is no object at the other focus of a planet's orbit. The semimajor axis, a, is half the major axis of the ellipse. In some sense it can be regarded as the average distance between the planet and its star, but it is not the time average in a strict sense, as more time is spent near apocentre than near pericentre.
http://en.wikipedia.org/wiki/Kepler's_laws_of_planetary_motion

As to the idea of free floating planets, according to this Wikipedia article, so far it's only hypothetical, and can be addressed when one is found.

An interstellar planet is a (so far hypothetical) type of rogue planet that has been ejected from its star system by a proto-gas giant to become an outcast, drifting in interstellar space. Possibly it formed on its own through gas cloud collapse like a star. It should be noted that many astronomers and astronomy organisations, including the IAU believe a body must orbit a star to be a classified as a planet, and that the term interstellar planet is thus an oxymoron.
http://en.wikipedia.org/wiki/Interstellar_planet

Even so, if such a planet would be found, it still wouldn't have Pluto's problem of being a member of a "belt" of objects. In Pluto's case a member of the Kuiper belt of objects beyond Neptune. Pluto is a Kuiper Belt Object, and the IAU is correct in not calling it a planet.

[Matt-hurricanewatcher]

I agree...As long as those worlds are named Darf pluto's in theres a place to look at them....I'm ok.

[kevin]

This is wrong.

All of the sudden planet means able to clear out a path? There are asteroids in our orbit, and in Jupiters, and in Neptune's. Pluto is essentially in Neptune's orbit, and wasn't cleared out. The definition is contradictory and arbitrary. It is not good science.

Blast it.

[Terrell]

This is wrong.

All of the sudden planet means able to clear out a path? There are asteroids in our orbit, and in Jupiters, and in Neptune's. Pluto is essentially in Neptune's orbit, and wasn't cleared out. The definition is contradictory and arbitrary. It is not good science.

Blast it.

Here's an explanation from the wikipedia article as to why things like Neptune (or Jupiter) which have other bodies in their oribial paths, but aren't really members of belts are still planets under the new definition of Planets, but Pluto isn't.

"Clearing the neighborhood"
Main article: Clear the neighborhood
The criterion of "clearing its neighborhood" is not without ambiguity. It is not entirely clear what "clearing the neighborhood" actually means. Alan Stern contends that, since neither Earth, nor Mars, nor Jupiter, nor Neptune have entirely cleared their regions of debris, that none could properly be considered planets. [14].

In his article on the subject, Steven Soter gives a clearer definition of what is meant by "clearing the neighborhood." Essentially, it is Mike Brown's definition by mass dominance: if an orbiting body is more than a hundred times more massive than the remaining collective mass in its "orbital zone", then it is a planet. Two bodies can be said to occupy the same "orbital zone" if their orbits cross a common distance from the star, or "primary", and their orbital periods differ less than an order of magnitude. In other words, if two bodies occupy the same distance from a star at one point in their orbits, and those orbits are similar, rather than, as a comet's would be, extending for several times the other's distance, then they are in the same orbital zone. [15]

Assuming this definition of "neighborhood" is the one ultimately accepted by the IAU, it is still not an unambiguous concept. It does not define a planet by composition or formation, but, effectively, by its location. Hence, by this definition, a body of Pluto's size or smaller orbiting in isolation would be called a planet, whereas larger objects in close proximity to one another would be termed "dwarf planets

http://en.wikipedia.org/wiki/Definition_of_planet#.22Clearing_the_neighborhood.22

If Pluto orbited solo then it would be a Planet, but since it's a member of the Kuiper Belt of similiar objects it's not a planet.

[Beam]

It's just a good idea to have a set criteria for planet classification, and to make an exception to this rule due to some emotional attachment to this classification just because it's been that way for a while is rather silly.

If we let a belt-member object like Pluto be classified as a planet, we'd also have to add Ceres, Vesta, Juno, Xena, Sedna, and perhaps Charon, in addition to dozens of other objects.

Until we can get a really nice look past the Kuiper Belt and see what's spining around out there, you're gonna have to live with only eight planets. You can keep calling Pluto one if you want, but won't be scientifically correct.

[vbhoutex]

I was fascinated by the planets and solar system as a child and even built a model exhibit of the planets for a science project, which of course Pluto was a part of it.

I agree brunota, Pluto will always be a planet for me too. that's just plain crazy talk.

Me too!

[Terrell]

Pluto has more in common with the other Kuiper Belt Objects (KBOs) than with the 8 planets based on what we currently know about it. Even with it's new classification, I still can't wait for New Horizons to arrive in 2015 to do it's flyby of the KBO and give us or first close up pictures of Pluto, Charon, Nix, and Hydra, who knows what else we'll find out, as these space probes, unless they fail mechanically, tend to find things we don't expect to find.

Maybe Pluto gets it's own version of the NEAR mission, at some time in the future (though it's possible that it may not be in our lifetimes) since something doesn't have to be a full fledged planet to get NASA's attention. Ion drive engines (which have been used in a mission before namely, Deep Space One) might help. I don't think that the change of it's status makes it any less interesting since it is still the 1st KBO that we ever discovered.

[kenl01]

I was fascinated by the planets and solar system as a child and even built a model exhibit of the planets for a science project, which of course Pluto was a part of it.

I agree brunota, Pluto will always be a planet for me too. that's just plain crazy talk.

Me too!

Gosh I wonder what's next ?? First someone said we have 12 planets a few weeks ago, now it's 8 planets ??

Next they'll be saying that earth is not a planet !!

[Terrell]

I was fascinated by the planets and solar system as a child and even built a model exhibit of the planets for a science project, which of course Pluto was a part of it.

I agree brunota, Pluto will always be a planet for me too. that's just plain crazy talk.

Me too!

Gosh I wonder what's next ?? First someone said we have 12 planets a few weeks ago, now it's 8 planets ??

Next they'll be saying that earth is not a planet !!

Problem with the definition that would give us 12 planets was that it essentially was anything big enough to be round that wasn't also a moon (except for Pluto's largest moon Charon due to their barycenter being outside Pluto) would qualify as a planet. The definition would result in way more than 12 things being planets. Those are just the 12 biggest objects mentioned.

An IAU statement admits to having "never officially defined what constitutes a planet." Furthermore, the IAU used "historical practice in accepting the eight planets that were known when the IAU was created and accepting Pluto as the ninth when it was discovered (in 1930) not long after the formation of the IAU."

For two years, Gibor Basri of the University of California, Berkeley, has been working on a formal definition of planets to propose to the IAU. In Basri's scheme, made public today, there are at least 12 planets known right now, and the tally would quickly rise beyond two dozen as more discoveries are made.

Most of these additional small worlds, some roughly half the size of Pluto, orbit at the fringes of our solar system in a region called the Kuiper Belt.

(emphasis mine)

Essentially this is a "leave no small ball of rock and ice behind" definition of planethood. Read the next paragraph to see just how many Kuiper Belt Objects have been detected so far. I could also add the Wikipedia entry on the issue, either under Pluto or the Kuiper Belt, Space.com says 600 KBOs Wiki says 800, that's a lot for the kiddies to memorize don't you think? Most of them are pretty big and since they're combos of rock and ice, bet lots of them are also round, so under that definition they're planets.

Basri would like to accommodate Pluto and those who can't fathom its demotion. He proposes that the murky lower limit for planet-hood get set at a diameter of about 435 miles (700 kilometers). That's roughly the bulk needed to allow gravity to shape an object into a sphere, depending on density. Smaller objects -- both asteroids and comets -- tend to look like potatoes or bell peppers.

If the size cutoff were accepted, two KBOs -- named Varuna and Quaoar -- would become instant planets. More would surely be added to the list each year as new discoveries are made. More than 600 KBOs have been detected so far, but researchers extrapolate the limited sky surveys done so far to estimate there are about 100,000 of them bigger than 62-miles (100 kilometers). Enough larger KBOs exist to grow the solar system's planet count, based on Basri's definition, to two dozen within two years, according to estimates.

The asteroid Ceres would also have to be reclassified as a planet under Basri's plan. At 930 kilometers (580 miles) wide the Texas-sized rock was the first asteroid ever discovered back in 1801. At the time, some astronomers thought it was a planet, until other asteroids were discovered. Like most other asteroids, Ceres orbits the Sun in a belt between Mars and Jupiter

(emphasis mine)

http://www.space.com/scienceastronomy/planet_denitions_030227.html

The above link applies to both quotes.


With a round object definition you can also welcome most of these objects to planet hood as well (Earth is shown for size comparison) 2003EL 61 would not qualify. source is wikipedia Pluto Page

http://en.wikipedia.org/wiki/Pluto#New_discoveries_ignite_debate
http://upload.wikimedia.org/wikipedia/c ... htTNOs.png
Updated image

Would like to use the smaller version, but I can't get the low resolution version to show anything other than a small red x.

[Terrell]

Update, 2003 UB 313 formally named Eris after the Greek goddess of Chaos and Strife. Her moon is named Dysnomia, daughter of Eris and the spirit of lawlessness.

http://news.yahoo.com/s/ap/20060914/ap_on_sc/dwarf_planet

Given the debates caused by her discovery, the name is very apropriate.